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Topic: Substrate and water retention (Read 16299 times)

Well, you can rationalize just about anything, especially if you can make a reasonable graphical representation!

As I inferred, I salute your efforts. However, I wouldn't draw many conclusions other than stuff in pots hold water. It is kind if like recording the temperature on a monday, tues,wed,thurs, fri, sat and a sunday. Then, making the statement "On Monday the temperature was 70 F, on Tuesday the temperature was 72,etc.,and then concluding "Tuesdays are warmer than Mondays."

Great little book out there that helps with these kinds of things, called "How to lie with Statistics", great examples of how graphs and figures can unintentionally lead to unusual interpretations.

Thanks Scott for stimulating a fun conversation!

Just here to help. And thanks for joining in, John - I appreciate healthy skepticism. But I have to ask - were you surprised by the inverse relationship between grain size and saturation? I agree that the simple tests I've done here prove nothing by themselves, but the relationship conforms to capillary theory and the values are not out of range of saturated porous media that I've worked with in the past.

Oh, just to be complete, the opposite is true as well. Based on the data shown, the differences that you claim can not be disproven either, without more data. Thus, it is kind that you have agreed to have your Droids replicate the experiment. I am not sure that 5000 replicates would be required, but an idea of the variability would add great insight.

Oh, just to be complete, the opposite is true as well. Based on the data shown, the differences that you claim can not be disproven either, without more data. Thus, it is kind that you have agreed to have your Droids replicate the experiment. I am not sure that 5000 replicates would be required, but an idea of the variability would add great insight.

It takes at least 5 replicates to be reasonably confident of the mean and over 30 for the dispersion about the mean (which would represent measurement errors, variation in the particles sizes in each category, and whatever else contributes to variability in the tests).

Actually, 5 would give you more information but it may or may not give any more confidence in the results. Since we do not know what the variability is for each point of measurement, we can not estimate the sample size necessary to separate the means among and between soil types or sizes. The variability due to the method appliedmay very well hide any differences due to soil size or composition. Sokol and Rohlf has a well defined formula to determine sample sizes required to detect differences, however you will need more data to estimate.

I have to confess that this has not been my "go to" bonsai source. But that may change as a result of this discussion. A while ago I had an urban yamadori opporutinity and dug about a dozen old boxwoods from someone's house. Needing something to put them in and not wanting to spend a fortune I did some quick research and settled on expanded shale mixed with organic material. But finding how cheap expanded shale is I decided to do an experiement of my own. So my methodology was completely different than Mary's. And the products tested, while overlapping, were quite different.

I first dried all the materials for 12 hours in a convection oven at 200 degrees. Then I weighed each product. Then I Submerged 500ml of each product in water for 24 hours. Finally, I drained the products and re-weighed. So let's recognize that my attempt at a test didn't appreciate particle size. Nor did it measure in any way water retentiveness over time, only initial retentiveness. But for what it's worth, here is a table with my results...

APL Akadama Expanded Shale Dyna Rok Pumicewt, dry 322 306 378 166 290

wt, 24 hr soak 436 436 462 386 398

Retain H2O ML 114 130 84 220 108

In this case APL is 1/3 Akadama double red line, 1/3 Pumice, 1/3 Lava

The take away for me is the performance of Dyna Rok as a retentive medium.

I love to see CEC info on any and all of the media discussed in this thread.

Judy Where do you get your haydite ? I was going to try it also and so I went to the local rockery where they also have a large concrete mixing plant and fill and deliver their own concrete. I walked in and asked if they had any haydite and they asked what is haydite. I explained it to them and there was no one in the whole place that had ever heard of it. A crowd had gathered by then and I was starting to fell a bit embarased thinking maybe I had confused my information. They were all very interested and promptly they looked it up on their computer. I finally felt vindicated when they found it and said they were going to do more research their self. Well, so now where can I get some, if the concrete people don't even know what it is?

I can drive up there and get it in bulk, for reasonable prices. There is a guy up there that sells a soil mix which has haydite, river rock, bark, and charcoal. I know he sells on ebay, and thru internet site, and his prices seem reasonable. I know he would just sell you straight haydite if you wanted it. The company name is The Bonsai Den.

Just in case anyone wants to know, been using our local crushed, sifted, porous, fired red earthenware brick since 1983 or so [ Seramis ?] as an ingredient in my bonsai soils. The other two ingredients are sifted silca based builder's gravel and compost.

If you added the brick to peat moss, at say 1/3, the peat moss is not really able to dry out, as the brick re-wets easily and immediately, also moisturizing the peat moss, and brick doesn't float.

Presently we are going through our drying out winds stage of the Dry Season, and I have to water once in the evening before 5.30 p.m and twice in the morning. Exposure is full sun, 6 to 6. Soil mix handles the gale force winds well - chuckle.

It is amusing to see from the Seramis website, all this excitement. Still the plant on the youtube example was not bare rooted.Hmm in the 1980's the Germans also marketed an expanded rounded clay as well for houseplant hydroponics.Back to transplanting and the temperature is still around 68 deg.F at night, the trees are still sleeping/dormant.From the tropics, good evening.Anthony

I am in the West Indies [ Caribbean ], and that should give you an idea of the range of temperatures found in the Tropics.For if I lived in Jamaica or Venzuela, I could see frost as well, and possibly snow -chuckle.Good Evening.Anthony.